We report the synthesis of branched acrylic copolymers based on 2-hydroxypropyl acrylate using reversible addition fragmentation chain transfer (RAFT) polymerization in tert-butanol at 80 °C. Three branching comonomers were investigated in this study:  ethylene glycol diacrylate, bisphenol A ethoxylated diacrylate and a disulfide-based diacrylate. The latter comonomer allows chemical degradation of the branched acrylic copolymers to produce thiol-functionalized primary chains. Gel permeation chromatography analysis of these degraded copolymer chains indicated low polydispersities (M w/M n < 1.22), which confirmed that the living character of the RAFT chemistry was retained under branching conditions. RAFT allows significantly more than one branching agent per primary chain to be used in the copolymerization without causing gelation. This result was obtained with all three branching comonomers and differs from the near-ideal copolymerizations previously reported for the ATRP synthesis of branched methacrylic copolymers (Macromolecules 2006, 39, 7483−7492). Detailed HPLC analysis of the RAFT copolymerization of 2-hydroxypropyl acrylate with bisphenol A ethoxylated diacrylate indicates near-statistical incorporation of the latter comonomer. We suggest that intramolecular cyclization is the primary reason for the apparent violation of classical Flory−Stockmayer gelation theory. This hypothesis is supported by the observation that substantially more ethylene glycol diacrylate than bisphenol A ethoxylated diacrylate can be tolerated in such branching copolymerizations without causing gelation.

Multiwalled carbon nanotubes (MWNTs) were oxidized with concentrated HNO3 and H2SO4 to introduce carboxylic groups onto MWNT surfaces. The oxidized MWNTs were reacted subsequently with thionyl chloride, glycol, and 2-bromo-2-methylpropionyl bromide, producing MWNT-based macroinitiators, MWNT-Br, for the atom transfer radical polymerization (ATRP) of glycerol monomethacrylate (GMA). In the presence of N,N,N‘,N‘ ‘,N‘ ‘-pentmethyldiethylenetriamine (PMDETA)/Cu(I)Br, hydroxyl-functional polyGMA, with weight concentration of ca. 50−90%, was successfully grown from the MWNT surface. Comparative experiments, with MWNT-Br and ethyl 2-bromoisobutyrate as co-initiators, showed that (1) the presence of free initiator has no significant effect on the nanotube-surface initiating polymerizations, (2) both the polymer content grafted on the nanotubes (46−88 wt %) and the number-average molecular weight (M n) of free polymer (3000−17 000) can be efficiently controlled by adjusting the feed ratio of monomer to co-initiators, and (3) the polydispersity index (PDI) of the free polymer increased when either the feed ratio or the molecular weight was increased. Further derivatization of the grafted polyGMA with succinic anhydride converted the hydroxyl groups into carboxylic acid groups. The resulting polymer-functionalized MWNTs were characterized with FTIR, 1H NMR, 13C NMR, TGA, SEM, and TEM. Furthermore, the poly(carboxylic acid)-modified MWNTs were used to sequester metal ions such as Ag+, Co2+, Ni2+, Au3+, La3+, and Y3+, forming MWNT-polymer/metal hybrid nanocomposites, nanowires, or necklace-like nanostructures, depending on the grafted polymer content and the nature of the captured metal. SEM and TEM studies combined with X-ray analyses confirmed the structure and elements of the novel hybrid nanoobjects. Interestingly, polymer enwrapped-silver nanobeads or nanodots with a diameter of ca. 3−10 nm decorating the convex surface of MWNTs were obtained. The synthesis, derivatization, and metal loading of functionalized MWNTs suggests a new route for rational molecular design and augurs well for future applications of functionalized nanomaterials, including device fabrication.

The one-pot synthesis of a new anionic polyelectrolytic macroinitiator based on esterification of a poly(glycerol monomethacrylate) precursor is described. Electrostatic adsorption of this macroinitiator onto an aminated (cationic) planar substrate is monitored by dual polarization interferometry. Controlled surface-initiated polymerization of five hydrophilic methacrylic monomers from this macroinitiator adsorbed onto aminated silicon wafer surfaces is achieved by atom transfer radical polymerization (ATRP) in protic media. The thickness, uniformity, and hydrophilicity of the resulting polymer brushes are characterized by ellipsometry, atomic force microscopy and contact angle studies, and the hydrophilic surface polymerization kinetics is modeled. Microcontact printing is used to produce patterned surfaces with micrometer-sized features. In summary, polyelectrolytic macroinitiators allow the facile synthesis of well-defined polymer brushes on commercially relevant metal oxide surfaces.